Though Christie's poll numbers aren't close to Trump's, they still represent a sharp turnaround as the governor has relentlessly campaigned in New Hampshire. Christie's campaign appeared to be on life support for much of the year, but New Hampshire voters seem to be giving him a second look.

The numbers also represent an obstacle for several other Republican hopefuls who have bet big on New Hampshire, an influential primary state that weighs in early. Former Florida Gov. Jeb Bush (R), Ohio Gov. John Kasich (R), and Sen. Lindsey Graham (R-South Carolina) are among the candidate who have focused on New Hampshire.

In the WBUR poll, Christie only narrowly edged out Sen. Marco Rubio (R-Florida), who had 11%, and Sen. Ted Cruz (R-Texas), with 10%. Bush and Kasich followed with 8% and 7%, respectively.

"The presence of Christie I think makes things more complicated for, let alone Jeb Bush and John Kasich, but also Marco Rubio emerging as the Trump alternative," University of New Hampshire political scholar Dante Scala told WBUR.

"And that's a key question: One, will the Trump vote be there in the end?" Scala asked. "And two, will the so-called establishment vote split half a dozen different ways?"